Detection, monitoring, and management of gas presence, gas flow and gas leaks in composites manufacturing

ABSTRACT

Porosity causing gas-based defects are detected, located, identified, and/or characterized by the use of defect information generated from gas flow data corresponding to gas flow characteristics measured by one or more sensors on a composite part processing piece such as a mold or membrane used during a composite manufacturing process. The defect information is generated using techniques including one or more of profiling the gas flow data, fingerprinting, line leak detection, analytical triangulation.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional PatentApplication No. 61/661,467 filed Jun. 19, 2012, entitled Detection,Monitoring, and Management of Gas Presence, Gas Flow and Gas Leaks inComposites Manufacturing.

FIELD OF THE INVENTION

This disclosure generally relates to methods for collecting andinterpreting industrial process data, and more specifically to a systemand method using in situ sensors to collect data during compositemanufacturing, including preparatory bagging and sealing, as well as theprocessing inside an autoclave, oven, press or other compositemanufacturing system.

BACKGROUND OF THE INVENTION

In composites manufacturing, the object is to produce the highestquality part possible. A common defect in composites is the presence ofvoids and porosity. Voids and porosity can be minimized by minimizingthe sources of gas leading to such voids and porosity, and maximizingthe removal and reduction of gas volume. Sources of the gas include butare not necessarily limited to entrapped air during preparation of thepart, entrapped moisture, and generation of gases as a by-product of thechemical reactions during cure of the matrix, and leaks during themanufacturing process. Regardless of the method of compositesmanufacturing, the removal of gas by the application of vacuum to thepart is a well-established procedure. It is generally accepted that asufficient vacuum must be pulled on a part to achieve good quality, andconsiderable time and effort is expended in managing and controlling thevacuum pulled on a part.

Current methods for assessing the vacuum pulled on a part in the mostpart involve the measurement of the gauge or absolute pressure in thevacuum lines. The lower the measured pressure, the better the vacuumpulled on the part. As it is known that the pathways into the part andwithin the part may be blocked, a variety of methods are used to ensurethat there are open pathways to every position in the part. Methodsinclude but are not limited to multiple vacuum lines, so-called‘breather’ fabrics, and specialized raw composite material forms such asso-called ‘out-of-autoclave’ pre-impregnated materials.

Leaks are a particularly common source of quality problems. Sources ofleaks include but are not limited to improper sealing of seams betweenmould segments, improper sealing of flexible vacuum bags over the partand mould, puncturing of the flexible vacuum bag, failure of rubber andother hollow inserts, and failure of the solid mould or semi-flexiblecaul plate. Leaks can be present from the beginning of the manufacturingprocess, or can occur later in the process, for example when heating orpressurizing the assembly inside an autoclave, oven, or press.

The most common methods for detecting the presence of leaks, oralternatively confirming the vacuum integrity of the system, consist ofshutting off the evacuation of the assembly, and monitoring the rise ofpressure as air leaks into the assembly. An increase in pressure lessthan a prescribed amount, over a prescribed time, is considered to beindication of adequate vacuum integrity. This procedure istime-consuming, particularly if a leak is found to be present, and theprocedure must be repeated after every attempt to fix the leak.Consequently the conventional leak detection method may take many hoursto locate a single leak, causing significant and costly manufacturingdowntime. Furthermore, the procedure is sensitive to the size of thepart, and the larger the part, the less sensitive the procedure. Othermethods, including sensitive coatings on the vacuum bag, and the use ofmass flow sensors for vacuum assisted resin transfer moulding, have alsobeen evaluated. Additionally, particularly in a very large part, thereis currently no simple way to identify even the approximate location ofthe leak, other than by compartmentalizing the part. Outside ofcomposites manufacturing, gas flow rates out of a system are oftenmonitored and used instead of, or with, gas pressure measurements. Afundamental problem to date has been that the relationship between gaspressure and gas flow rates is complex.

Accordingly, there is a need for a system that provides continuoususable information on the evacuation state of the assembly (includingduring cure), and in the case of a leak, allows for immediate andcontinuous monitoring of the leak, including preferably guidance as tothe location of the leak and its significance.

In the prior art applicant is aware of U.S. Pat. No. 3,818,752 whichissued to Lindeberg on Jun. 25, 1974 for A Method And Apparatus ForTesting Tightness. Lindeberg describes the use of pressure differentialacross a valve for detecting leaks in an enclosed volume wherein, afterthe pressure difference across the valve falls below a predeterminedvalue, any further flow that is sensed is indicative of a leak in thevolume. Lindeberg also discloses that if a leak is detected, thelocation of the leak may be obtained by smearing the volume tank with asoap solution or the like so as to provide an indication of where air orliquid is forced out of the tank.

Applicants are also aware of United States Published Patent Application,Publication No. US2008/0252470, which published on Oct. 16, 2008 in theapplication of Taricco entitled Leak Detectors and Leak DetectionMethods. Taricco describes that it may be necessary in the field ofcomposite structure manufacturing to leave a pressure or vacuum on asystem for a prolonged period without loss of pressure or vacuum as aleak test. A vacuum sensing and alarm system is disclosed by Taricco asbeing used together with a pressure gauge, separate or integral with thesystem, wherein the pressure gauge would confirm that the pressure orvacuum remained within acceptable limits throughout the prolongedperiod. An adjustable pressure of vacuum switch detects a more rapidleak. Alternatively the pressure switch may be replaced by a pressuretransducer.

Applicants are also aware of United States published patent application,Publication No. US2009/0273107 which published Nov. 5, 2009 in theapplication of Advani et al. entitled System and Method Of Detecting AirLeakage in A VARTM Process. Advani et al. disclose using heated air anddistributing the heated air along an interface along a bagging film andthe surface of a mould so as to locate leaks in the bagging film bydetermining the temperature distribution of the air along the interface.Advani et al. describe that during the VARTM Process that checking thevacuum level is standard procedure especially when a large part is beingmade, as any air leakage will decrease the part quality. Advani et al.further disclose that the primary leak isolation method which isconventionally used is performed by vacuuming the air out of the mouldand if the vacuum pressure level has not decreased after a predeterminedamount of time that the mould is considered to be free of air leaks, butthat the disadvantage of this method is that it is only able to indicateif there is or is not a leak and does not specify the location of anyleak. Thus Advani et al. teach using thermal leak detection employing aheat gun to warm air and introduce that warm air to potential leak areasaround the mould, and that the method may also utilize a infrared camerato capture thermal images of the tested areas.

Applicants are also aware of United States published patent application,Publication No. 2010/0326584, which published on Dec. 30, 2010 in theapplication of Schibsbye entitled Method and Apparatus for DetectingLeak in A VARTM Process. Schibsbye discloses that during producing acomposite structure, and in particular during the evacuation process, anair flow level through at least one vacuum outlet is measured. Schibsbyedescribes a method for manufacturing a composite structure whichincludes fibre reinforced material using a vacuum assisted resintransfer moulding process wherein the fibre material is impregnated withliquid resin. Schibsbye identifies a problem in the VARTM processwherein dry spots where the fibre material is not impregnated with resinprovide areas for air pockets which need to be repaired. Schibsbye alsoidentifies that leaks in the sealing between the mould part and thevacuum bag and/or in the vacuum bag itself may lead to problems witheffectively evacuating the mould cavity or effectively filling the mouldcavity with resin, thereby also being a cause of dry spots. Schibsbyestates that even very small holes can cause these problems, and as fibrecomposite structures, such as wind turbine blades may have a length of60 meters and have a surface area of several hundred square meters, thatit can be very time consuming to find the leaks thereby prolonging theoverall production time of the laminate structure.

Consequently, Schibsbye proposes the use of a gas mass flow sensorconnected to an inlet tube in order to measure the gas flow through theinterior of the container. A pressure transducer is provided so as tomonitor the vacuum level, that is, the pressure in the interior of thesealed container and consequently the vacuum level of the mould cavityor the individual mould cavity sections. If it is determined that thegas flow for a given apparatus exceeds a predetermined threshold valuefor a given vacuum level, then the operator knows that a leak exists inthe mould cavity, and if only a single apparatus identifies such a leakthen it can be concluded that the leak exists in the corresponding mouldcavity section. Schibsbye teaches that by using flow sensors an operatorof the VARTM process can identify leaks and the location of such leaksfaster.

Finally, applicants are aware of three United States publishedapplications having a common inventor; namely, Miller, and a commonassignee; namely, the Boeing Company. Thus in United States publishedpatent application, Publication No. US2008/0148817, published Jun. 26,2008, in the application of Miller et al. entitled Leak Detection InVacuum Bags, the use of a leak detection film covering the inside faceof the vacuum bag is disclosed wherein the film includes a gas permeablebinder carrying oxygen sensitive material that changes in physicalappearance at the location of an air leak. Miller et al. discuss thatflexible vacuum bags are used in manufacturing such as the fabricationof composite structures and the bonding of parts, for example, in theaerospace industry where vacuum bags may be used in vacuum bag mouldingwherein a flexible bag is placed over a part pre-form and sealed along amould flange. Air is evacuated and liquid resin is drawn into the bagwhich is infused into the pre-form so that any leaks in the vacuum bagmay allow air to enter and form bubbles in the resin matrix resulting inan unacceptable amount of porosity in the matrix.

Thus Miller et al. propose that leaks may be detected in gasimpermeable, transparent membranes used to maintain a pressuredifferential by the use of a gas permeable film or coating placed on ornear the membrane that emits or reflects light of various wavelengths inthe area of the leak or pressure gradient so as to provide rapid visualdetection of air leaks in vacuum bags. The gas sensitive materialchanges in appearance in response to exposure to gas caused by a leak inthe bag.

In United States published patent application, Publication No.US2010/0170326, published Jul. 8, 2010, in the application of Miller etal. entitled Leak Detection In Composite Tools, which is acontinuation-in-part of the aforementioned application to Miller et al.,Miller et al. state that, although a vacuum integrity test may provide ameans to indicate the presence of a leak, the vacuum integrity test maylack the capability to allow for identifying the location of leaks onthe tool, and that another draw back is that the vacuum drop check maynot provide an indication as to whether the leak is in the tool, in thevacuum bag, or in the seal that seals the vacuum bag to the tool. Milleret al. propose the use of a breather layer interposed between the tooland the leak detection film for facilitating air flow therebetween.

In United States published patent application, Publication No.US2011/0259086, published Oct. 27, 2011, in the application of Miller etal. entitled Leak Detection in Vacuum Bags, a device is described forindicating the location of an air leak in a vacuum bag used to processcomposite parts. The device includes a layer of material on the innerface of the bag that changes in appearance due to an oxidation-reductionreaction in the areas of the layer exposed to oxygen caused by a leak inthe bag. Miller et al. describe the use of an ink or dye which isapplied to the inner face of the vacuum bag film, wherein once a vacuumis drawn within the bag causing the air pressure within the bag to dropwhich then allows the atmospheric pressure to push the bag down onto thelayup and to compact the layup, the colorimetric material is activatedby directing ultraviolet light through the transparent vacuum bag andonto the ink rendering the ink reactive to oxygen so that the inkchanges in color when exposed to oxygen due to a leak.

SUMMARY OF THE INVENTION

In the present invention, one or more in-situ thermal mass flow sensorsare provided. Each may be packaged with one or more other sensors into a‘sensor package’, to monitor gas flow in composite manufacturingprocesses, including but not limited to autoclave and oven manufacturingof pre-impregnated material structures made of both thermoset andthermoplastic materials; and resin infusion or resin transfer mouldingprocesses. For example, multiple sensor packages may be used to senseflow rates at multiple locations, such as within the breather, vacuumports, vacuum hoses, and bladder vents. In one embodiment the inventionreduces the ambiguity and cost of leak check data based on pressure risemeasurements or other methods, allow for identification of the locationof the leak, and speeds up the process of leak detection and repair.Additionally, the flow rate profiles, including the shape of theevacuation profile, and the integral of the flow rate, i.e., the totalvolume of gas evacuated, may be used to evaluate the consistency of thepart manufactured relative to the general population of partsmanufacture, allowing for the use of statistical and data miningtechniques to assess production. Additional capabilities in terms ofidentification of moisture outgassing and other features are furthersummarized and described below.

In summary, the present invention may be characterized, in one aspect,as a process for manufacturing a composite part, wherein during theprocess the part is engaged by a gas impermeable part-processing piecechosen from at least one of the group comprising: an upper or lowermould or tool, wherein the terms mould or tool or tooling are usedinterchangeably herein, a rigid or semi-rigid caul plate, a membrane, avacuum bag, a bladder, and wherein the part processing piece hasopposite inner and outer surfaces.

In the process, when the membrane is either a vacuum bag or a bladder:(i) the vacuum bag defines a flexible non-compartmentalized singlevolume containing or covering the part and the process is a vacuumprocess which includes evacuating the volume to low pressure; or, (ii)the bladder defines a flexible non-compartmentalized single volumecontained in or covered by the part and the process is a pressurizationprocess which includes pressurizing the volume.

The process includes identifying a porosity-causing gas-based defect,wherein the gas based defect includes one or more defects from the groupcomprising:

-   -   a) previously entrapped gas entrapped in the part or in the        volume, for example between the part and the mould or membrane        or other part-processing piece,    -   b) gas generated during a process cycle of the manufacturing of        the part due to moisture off-gassing or volatile evolution due        to the chemical changes in the part during a curing of the part,    -   c) at least one gas leak.

The process may include the steps of:

-   -   a) providing the part-processing piece and at least one gas        conduit, said at least one gas conduit cooperating in fluid        communication with said part-processing piece for flow of gas        through said part-processing piece,    -   b) mounting the part-processing piece so as to engage the part        so that, respectively, the part is within a volume defined by        the part-processing piece when it is around or over the part, or        so that the part contains within or under it, so as to be        pressurized by, the part-processing piece when it is contained        in or covered by the part,    -   c) providing at least one sensor mounted in cooperation with the        part-processing piece, and wherein, when the at least one sensor        is a plurality of sensors, the sensors are mounted in spaced        apart array relative to the part when in, under or containing        the part-processing piece, and wherein the sensors are in fluid        communication with the volume and wherein the at least one        sensor is, or the plurality of sensors are, adapted to detect        and measure at least one characteristic of a gas flow as a        result of the gas-based defect,        -   and in a preferred embodiment the process includes the            following steps:    -   d) during the vacuum process or the pressurization process,        respectively evacuating the volume or pressurizing the volume,    -   e) detecting and measuring the at least one characteristic of        the gas flow during and after the evacuating or pressurizing of        the volume, wherein the at least one characteristic of the gas        flow includes one or more characteristics from the group        comprising: mass flow rate, temperature, pressure, moisture        content, and may include a chemical content of at least one        selectively detectable chemical, a spectrographically detectable        content,    -   f) generating gas flow data corresponding to the detecting and        measuring of the at least one characteristic of the gas flow,    -   g) computing defect information from the gas flow data by        computing the defect information according to at least one        computation technique chosen from the group comprising        computing: a profile over time of the gas flow data, gas flow        rate profile, gas evacuation profile, gas pressurization        profile, gas flow volume, fingerprinting, analytical        triangulation, gas flow rate vs. pressure, flow rate vs.        temperature, moisture vs. temperature, flow rate vs. rate of        pressure change.

The process may include relaying feedback of the defect information.

The feedback may, at least in part, be based on a spatial relationshipbetween a user receiving said feedback and said mould or membrane.

The defect information may include predicted leak locations and mayinclude a predicted leak type.

The fingerprinting may include recording the gas flow data and creatingand maintaining a historical record of the gas flow data. Thefingerprinting may include leak locations correlated to a physicalspecification of the part for each unique part.

The fingerprinting may also include computational fingerprinting, whichmay include creating a grid of virtual gas leak locations employing ageometry of the part and locations of the sensors relative to the part,and for each location calculating at least the gas flow rate profile fora predetermined flow rate of the gas leak to provide predicted defectinformation and comparing to the historical records and determining aclosest match and thereby a corresponding predicted gas leak location.

The fingerprinting may also include test-based fingerprinting, which mayinclude creating a grid of representative gas leak locations employing ageometry of the part and locations of the sensors relative to the part,and for each gas leak location creating a resealable and measurable gasleak and recording corresponding gas flow data for each location toprovide the historical record of the defect information for the part,and comparing the gas flow data and the defect information of thedetected and measured at least one characteristic of the gas flow to thehistorical record for the part to determine a closest match and therebya corresponding predicted gas leak location or corresponding predictedgas leak locations.

The fingerprinting may include recording the gas flow rate profile aspart of the historical record for each unique part. Where the process isa vacuum process, the fingerprinting may include recording the gasevacuation profile as part of the historical record for each uniquepart.

The line leak prediction may include providing the plurality of sensorsin substantially a linear array in correspondingly substantiallylinearly aligned locations, fitting a curve to the gas flow data and thelocations of the plurality of sensors, determining peaks in the curveand correlating the peaks to predicted locations of the at least one gasleak.

The analytical triangulation may include determining combinations ofpairs of sensors by employing a geometry of the part and locations ofthe sensors relative to the part, and for each pair of sensorsdetermining corresponding triangle apexes for all triangles from eachpair of sensors. For each pair of sensors, a base leg of the triangleextends to and between the pair of sensors, and a remaining two legs ofthe triangle define an apex therebetween at the intersection thereof.The remaining two legs have first and second lengths respectively inproportion to corresponding first and second gas flow rates at the pairof sensors respectively so as to determine for each pair of sensors acorresponding set of the triangle apexes to thereby provide acorresponding apex set for the pair of sensors. For each apex setdetermining either: (a) a point of intersection between the apex sets;or, (b) where there is no point of intersection, a mid-point of a linejoining points closest to one another between all of the apexes toprovide possible leak locations. The average of the possible leaklocations may be computed to thereby predict a single leak location.

The relaying of feedback may include displaying the defect informationto a user while the user is inspecting the part and the mould ormembrane. The defect information may thus usefully include a predictedlocation computed for the at least one gas leak.

The at least one sensor is advantageously mounted in fluid communicationwith the at least one gas conduit. The at least one sensor may includeat least one sensor from the group comprising: mass flow sensors, radialflow direction sensors, pressure sensors, differential pressure sensors,temperature sensors, humidity or moisture sensors. From that group, theat least one sensor may include at least all of the following sensors:mass flow sensors, pressure sensors and differential pressure sensors. Asensor package may be provided wherein the sensor package includes atleast two of the sensors from the groups within the package, and mayinclude all of the following sensors: mass flow sensors, pressuresensors and differential pressure sensors.

At least one of the sensors may be mounted between the part and theinner surface of the mould or membrane. Breather material may beprovided between the part and the inner surface of the mould ormembrane, wherein the breather material has substantially uniformpermeability. At least one sensor may be mounted on or in at least oneof the group comprising: at least one gas conduit, gas ports, a gasbreather, a mat having sensor flow passages.

A flow bypass may be provided cooperating with the sensors to reduce apressure drop across at least one of the sensors. The bypass may includea resilient flexible bypass valve member. The bypass valve member mayinclude a reed means, which may be biased between open and closedpositions, according to a pre-determined pressure threshold, by a gaspressure of the gas flow. The pressure threshold may be a differentialpressure threshold of a differential pressure across an associatedsensor. The bypass may be maintained in its closed position by amagnetic field.

The step of providing at least one gas conduit may include providing aplurality of gas conduits spaced apart and mounted on, in fluidcommunication through, the mould or membrane, and optimizing the sensorson the gas conduits for use with each type of uniquely shaped part. Theoptimizing may include applying the evacuation or pressurization of thevolume respectively during the vacuum or pressurization process via thegas conduits, and detecting and measuring the characteristics of the gasflow in the gas conduits, and subsequently correspondingly determiningthe defect information, when at least a first of the gas conduits arebiased into an open-to-gas flow condition and at least a second of thegas conduits are biased into a closed-to-gas flow condition. The biasingof the at least first and at least second of the conduits into theopen-to-gas flow and the closed-to-gas flow conditions respectively maybe cycled through all of the gas conduits in a pattern of opening andclosing of the gas conduits to the gas flow in substantially allpermutations as between substantially all combinations of opening andclosing of the gas conduits. The pattern may be predetermined. Further,the gas conduits may be located on the mould or membrane according tosensitivity information derived from the defect information, whereby arequired number of the sensors is minimized, and sensitivity to thegas-based defects is maximized.

In one embodiment the moulds or tooling may include a manifold, whereineither the moulds or tooling or the manifold are “smart” as definedherein.

In one embodiment the flow bypass is mounted in fluid communication withat least one conduit, so as to be separate from, that is, not in fluidcommunication with a sensor.

Advantageously, in the bypass the reed means may include a curved reed,that is wherein said curved reed is curved so as to elastically pre-loadthe reed when in the closed position.

In one embodiment the gas flow sensors are adapted to measure the flowof gas both into and out of the mould or membrane.

Each gas conduit may include a corresponding inlet and/or outlet filter.

In the leak detection method, in one embodiment the gas is other thanair so as to perturb the gas flow data. For example the gas may be CO₂or dry N₂. In the latter, the sensor(s) would include a moisture sensor.

In a further embodiment, a second vacuum system is provided which isindependent of the gas conduits used for the primary vacuum process. Thesecond vacuum system is mounted in a second, independent, fluidcommunication with said membrane. The second vacuum system is used tolocally reduce or increase, that is, to change the pressure in saidmembrane so as to change the flow rate of the flow of gas through thegas conduits for the primary vacuum process and thus so as to change theflow rate of the flow of gas interacting with the sensor.

In a further embodiment each gas conduit or gas port has a correspondingunique identifier so as to correlate the gas flow data with saidcorresponding unique identifier. The unique identifier may identify aunique location and may be chosen from the group which includes, forexample, barcode, or radio-frequency identification.

In a further embodiment at least one gas conduit may be adapted to carrypower and/or data.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying Figures like reference numerals denote correspondingparts in each view, and wherein:

FIG. 1 is a schematic representation of void generation and dissipation.

FIG. 1a is, in perspective view, an aircraft wing being manufactured bythe composite manufacturing process.

FIG. 1b is the schematic of FIG. 1 showing the use of a secondary vacuumsystem.

FIG. 2 is a schematic representation of a basic embodiment of a gasresponse measurement system.

FIG. 2a is a diagrammatic representation of a computer system used inconjunction with the system of FIG. 2.

FIG. 3 is a block diagram of one embodiment of a sensor package.

FIG. 3a is a block diagram of another embodiment of a sensor package.

FIG. 4 is, in perspective view, one embodiment of a smart manifold.

FIG. 5 illustrates the creation of a small pin hole leak on a simulatedbag on a test bed.

FIG. 6 illustrates the immediate response from flow sensors (withbypass) during the evacuation of the test arrangement of FIG. 5.

FIG. 7 illustrates the indication from the flow sensors that thesimulated bag of FIG. 5 is fully evacuated and no leaks are present.

FIG. 8 illustrates that the leak created in FIG. 5 is immediately sensedby the flow sensors.

FIG. 9 illustrates the prediction of the leak location in FIG. 5.

FIG. 10 is a graph of the effect of flow bypass on part pressure profileand speed of evacuation.

FIG. 11 is a graph of the effect of flow bypass on part pressure profileshowing that without bypass the part pressure remains high in thepresence of a large leak.

FIG. 12 is, in a cross sectional view, a schematic of a bypass having areed valve.

FIG. 13 is a block diagram of a high temperature (and optionally highpressure) sensor package.

FIG. 14 is, in perspective view, an example of the use of a sensorpackage on an insert such as a bladder.

FIG. 15 is an example of the use of under-bag flow sensors.

FIG. 15a is an example of a vacuum port probe with directional radialflow sensors.

FIG. 16 is an example of sensors installed within the moulds or tooling.

FIG. 17 is a high level schematic of system operation illustratingsoftware flow.

FIG. 18a is a schematic of system operation illustrating signal/datamonitoring.

FIG. 18b is a schematic of system operation illustrating leaklocalization.

FIG. 19 is a schematic of system operation illustrating trend analysisand fingerprinting.

FIG. 20 is a schematic of system operation illustrating real timeprocess simulation.

FIG. 21 is a schematic of system operation illustrating process control.

FIG. 22 is a schematic of system operation illustrating systemarchitecture.

FIG. 23 is a schematic of computational fingerprinting.

FIG. 24 is a schematic of line leak prediction.

FIG. 25 is a schematic of analytical triangulation.

FIG. 26 is a schematic of test-based fingerprinting.

FIG. 27 is a schematic of leak identification optimization.

FIG. 28 is a schematic of leak fingerprint database optimization.

FIG. 29 is a schematic of vacuum line and flow sensor locationoptimization.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

A schematic representation of void generation and dissipation is shownin FIG. 1. A vacuum bag or member 10 overlays a breather layer 12, whichoverlaps a release film 14. Release film 14 overlaps layers of pre-preg16 which have been laid-up on tool or mould 18. As used herein, the termpre-preg refers to pre-impregnated composite fibres where a pre-cured orpartially cured matrix bonding material, such as epoxy, is alreadypresent. These usually take the form of a weave or are uni-directional.Gas filled voids may be formed within pre-preg 16, caused by for exampleentrapped air 20 a, volatiles or off-gasing 20 b, or leaks 20 c in bag10, tool or mould 18, etc. Gas transport may be co-planar within orinterleaved between the various layers as shown by arrows A, or may beorthogonal to the layers as shown by arrows B. Collectively the gasmigrates to the vacuum source, indicated in FIG. 1 by arrow C leading tovacuum pump 22. Arrows D indicate void shrinkage or collapse.

FIG. 1a illustrates a worker 24 standing by a larger part 26;illustrated by way of example to be an aircraft wing, which is beingformed by the composites manufacturing methods to which thisspecification is directed. Thus it will be understood that the parts 26being formed may be very large and consequently have very large surfaceareas.

A diagrammatic layout of a basic embodiment of the hardware systemaccording to aspects of the present invention is shown in FIG. 2. Eachsensor package 28 is connected to a vacuum line or hose 30, for exampleis mounted in-line with a line or hose 30. Sensor package 28 may have avariety of individual sensors inside; for example: mass flow sensors,absolute pressure sensors, differential pressure sensors, temperaturesensors, moisture sensors, valve position sensors, chemical sensors, orspectroscopic sensors such as fourier transform infrared spectroscopicsensors or near-infrared spectroscopic sensors. Vacuum hoses 30 areconnected to vacuum pumps 22.

As seen in FIG. 1b , in a further embodiment, a second vacuum system isprovided which is independent of the gas conduits used for the primaryvacuum process. The second vacuum system is mounted in a second,independent, fluid communication with the membrane 10 a. The secondvacuum system is used to locally reduce or increase, that is, to changethe pressure in said membrane 10 a so as to change the flow rate of theflow of gas through the gas conduits 30 for the primary vacuum processand thus so as to change the flow rate of the flow of gas interactingwith the sensor. Thus, secondary membrane 10 a is mounted locally overvacuum bag 10 and independently evacuated via secondary hose 30 a bysecondary vacuum pump 22 a. Gas such as air between membrane 10 and 10 aflows in direction E in the case where the pressure between membrane 10and 10 a is reduced to affect the rate of flow in direction C throughhose 30.

As seen in FIG. 2a , each sensor package 28 communicates, via wired orwireless transmission, singly or as a group, with a back-end database 32that stores all the information from the sensors. Two examples of sensorpackages 28 are shown in FIGS. 3 and 3 a. Back-end database 32 is seenin FIG. 2a interrogated by one or more front-end applications forreal-time information during the manufacturing process as well as forhistorical and data mining information, as hereinafter described, aftera given part 26 is made. The front-end application can run on the samecomputer as the back end application and/or a front end computer 34 ormultiple other computers. The front end application and the back endapplication may be separate applications, a single combined application,or a mixture thereof. In one embodiment, a roamer mobile computer 36 orother portable data processing device may be carried by one or moreworkers so that the worker(s) receive feedback or provide input to or tocontrol the system as they work their way around a part 26 looking forleaks. Such a device may be a wireless device including but not limitedto a cell phone, tablet, mobile computer, etc. to display data such asvalues, plots, diagrams, images sent by the system, to provide input tothe system, and to control the behaviour of the system start/stop ofdata collection, to change system operating parameters, etc. The amountof interactivity between the system and the wireless device varies withthe capability of both the device and the system.

Although the illustration in FIG. 2 shows the schematics with sensorpackages 28 only on the vacuum hoses 30 and/or ports, sensor packages 28may also be mounted in the breather 12, such as by means of a breathermat that has multiple passages, wherein flow sensors may be mounted inthe passages. The mat is placed between the part and vacuum portsproviding under-bag flow sensing. Alternatively, sensor package(s) 28may be part of the tool or mould (so-called “smart” tooling), so thatmanifold style vacuum lines may be set up, or may be part of a “smart”manifold such as seen by way of example in FIG. 4. Smart tooling allowsthe moulds or tooling 18 to have multiple vacuum port locations whilevacuum is pulled from one location. Furthermore, in parts with internalcavities or volumes such as bladders, the sensors packages may measuregas transport into these cavities.

As seen in FIG. 4, smart manifold 29 includes a housing 29 a which maybe compartmentalized pr modular for having sensor packages 18 associatedwith each flow inlet 29 b. Hose 30 connect to inlets 29 b. The sensorpackages 28 may include inlet filters 29 c and outlet filters 29 d (seenin FIG. 3), sensors such as described herein below, including forexample flow sensors, pressure sensors, etc., and may alsoadvantageously include bypass valves as described below, dataacquisition modules, communication modules and a battery or batteries toprovide power to the modules. Flow from inlets 29 c exits from one ormore flow outlets 29 e.

The location of one or more leaks may be identified by triangulatingmeasured flow rates from different vacuum lines 30. This works very wellfor many geometries but in very complex shapes this is more difficult,and therefore the simple triangulation may be augmented byfingerprinting and learning methods, discussed below, where the systemis trained for a particular part, including the bagging and otherrelevant details. As described below, this learning may be empirical (byintroducing known leaks), analytical (by doing computer simulations) ora combination.

To provide additional leak localization capability, the positioning ofthe vacuum lines 30 may be optimized for this purpose, by placingstrategically placed vacuum lines 30 with sensor packages 28 to identifyleak locations more accurately. Given that often the leak problem is dueto hoses and fittings, multiple sensor packages 28 may also be placedalong a vacuum path, from part 26 to vacuum pump 22. In a system withmultiple vacuum lines 30 equipped with sensor packages 28, vacuum lines30 may be switched on or off individually or in groups, and the sensordata analyzed for patterns assisting in characterizing or localizingleaks.

An example of leak localization is described below using the testarrangement illustrated in FIG. 5, wherein a simulated vacuum bag 10 wassealed down onto a test bench (not shown). Vacuum hoses 30 were coupledto the four corners of the simulated vacuum bag 10 and a vacuum wasapplied to hoses 30. As seen in FIG. 6 the mass flow rate for each ofthe four hoses 30 was monitored and plotted as the volume between thesimulated vacuum bag 10 and the test bench was evacuated. The flow-rateover time plot of FIG. 7 confirmed that there were no leaks, as the massflow rate fell to zero and remained at zero. A pin hole was then made inthe simulated vacuum bag 10 so as to create a pinhole leak 38 ofapproximately two inches of mercury pressure drop per minute. As seen inFIG. 8, pinhole leak 38 was immediately sensed by the flow sensors oneach of the four hoses 30, with flow being indicated from all fourvacuum lines 30 commencing at substantially the same time. FIG. 9 showsthe results of the software (discussed below) predicting that thelocation of leak 38 was within area 38 a. As may be seen, the predictedlocation of the leak was very close to the known location of the actualleak 38. With sufficient sensor packages 28 and vacuum lines 30,multiple simultaneous leaks may be identified and located.

In the leak detection method, in one embodiment the gas is other thanair so as to perturb the gas flow data. For example the gas may be CO₂or dry N₂. In the latter, the sensor(s) would include a moisture sensor.

The sensor packages 28 are unique as compared to the prior art of whichapplicant is aware in a number of ways:

With regard to the use of inline mass flow sensors 40, appropriatelyselected and calibrated mass flow sensors 40 may be accurately used in aquantitative manner at the low absolute pressures (high vacuums) andhigh temperatures typically used in composites manufacturing. This isparticularly true for composite manufacturing processes other thanvacuum assisted resin transfer moulding (VARTM).

It is advantageous to include not only mass flow sensors 40, pressuresensors 42 and, optionally, temperature sensors 44, but alsodifferential pressure sensors 46 to know how much resistance the sensorpackage 28 is introducing into the vacuum system. Block diagrams of twosuch sensor packages 28 are shown in FIGS. 3 and 3 a. The use of adifferential pressure sensor 46 ensures that the mere presence of thesensor package 28 does not harm the part.

The gas flow characteristics measured by sensor packages 28 are used togenerate the gas flow data, such as the shape of the curve or profile ofthe gas flow vs. time, or pressure vs. time, etc. graphs as seen forexample in FIGS. 8 and 10 respectively. The profiles are ‘fingerprints’of a particular part 26 and can be used to identify, characterize, andrank the response of a given part 26, even before the part has beencompletely evacuated. Other data manipulation, including the integrationof the gas flow history (with appropriate zeroing and base lining), mayprovide invaluable insight into the performance of the part duringmanufacturing.

Defect information may be used to identify not only gas based defectsand leaks, but also features such as bag bridging, misalignment ofmoulds or tooling, caul plates, and other features, as well as excessivegaps and other unacceptable features.

Inline mass flow sensors 40 constrict the flow significantly, andtherefore may create unacceptable pressure drops across the sensor athigh flow rates. This has two distinct disadvantages: (a) longerevacuation times as illustrated in FIG. 10, and (b) unacceptablepressure increase across the sensor in the case of a leak as illustratedin FIG. 11. Therefore, a bypass which includes a bypass valve 48 such asseen in FIG. 12 may be advantageously employed in certain embodiments ofsensor package 28. At high gas flow rates, the bypass valve 48 opens,and the pressure drop across the sensor package is acceptably small asseen in FIGS. 10 and 11. Gas flow rates may still be measured by carefulcalibration and use of both the gas flow rate measurement and thedifferential pressure loss across the sensor package. At low gas flowrates the bypass valve 48 closes, and all of the gas flows through thegas mass flow sensor 40.

One bypass embodiment such as seen in FIG. 12, and which is not intendedto be limiting, may use one or more magnets 50 or other source(s) of amagnetic field to preload a reed 52, shown in the open position, that,when in its closed position, closes the bypass valve 48. In theillustrated embodiment bypass valve 48 has a housing or body 54 havingan inlet 54 a and an outlet 54 b. A conduit 54 c extends between theinlet and outlet. Conduit 54 c has magnets 50 mounted at the upstreamside of conduit 54 c. Reed 52 and flexible stopper 56 overlay thedownstream end of conduit 54 c so as to close conduit 54 c when valve 48is closed. Stopper 56 and/or reed 52 are made of or contain materialwhich is magnetically attracted to magnets 50, so that when stopper 56and reed 52 are in their closed position overlaying conduit 54 c so asto close off flow therethrough, a threshold pressure must be reached ininlet 54 a to overcome the magnetic latching of stopper 56 and reed 52over conduit 54 c. Once the magnetic latch is overcome by the pressurein inlet 54 a reaching the threshold pressure for the latch to open,flexible reed 52 and stopper 56 abruptly swing or bend to their openposition illustrated, that is, a substantially fully open positionthereby allowing gas flow through conduit 54 c. Thus, once the pressureincreases to a critical value due to too much flow, reed 52 releasesfrom magnet 50 and jumps to its open position, quickly dropping thepressure and resistance significantly. This is useful in a situationwhere there is a high flow rate from a leak, so that the sensor packagedoes not introduce harm to the part by keeping the part pressure high.Additionally, although bulkier, it may be desirable to have activebypass control using solenoid valves (not shown). Other forms of bypassor bypass valves would also work as would be known to one skilled in theart.

In the bypass design of FIG. 12, the reed valve is sized to achieve thedesired opening and closing behaviour. The crisp opening and closing ofreed 52 is determined by the magnetic field and strength of the magnets50, and by the flexibility of the reed. An electro magnet may also beused to allow the reed valve's behaviour to be actively controlled.Optionally, the reed may be elastically loaded when in it's closed, noflow condition, so as to snap open once released. Flow sensors, pressuresensors, differential pressure sensors, temperature sensors, and/or avalve position sensor may be usefully included. Stop 56 is optional, andis used to limit the deflection of reed 52. Reed 52 is advantageously oflight weight construction so as to minimize variation in valve behaviourwith orientation due to gravity, so that valve performance isindependent of the spatial orientation of the sensor package.Optionally, the reed's free end may be curved, for example to assist inloading reed 52 elastically when in its closed position.

By combining an appropriately calibrated moisture sensor 58 in eitherthe same sensor package 28 or in a coupled package, the water vapourmass flow rate may be calculated at the same time as the total gas massflow rate. The history of the water vapour mass flow rate may bemanipulated in the same manner as the manipulation of the total gas massflow rate discussed above. The combined analysis of total and watervapour mass flow rate may be used in decision making as described in thesystem level descriptions below. Instead of moisture sensors 58, otherchemical sensors, typically micro-electro-mechanical (MEMS) based, mayalso be used in similar fashion, providing additional datainterpretation opportunities.

A high temperature, high pressure resistant sensor package 28′ such asseen in FIG. 13 may be employed so that the measurements may be madeduring the manufacturing cycle, and not just during thebagging/preparation phase. The sensor packages 28 can be placed eitheroutside the oven or autoclave, and thus see lower temperatures and/orpressure, or if suitably ‘hardened’, as for example in the embodiment ofsensor package 28, may be placed inside the oven or autoclave, directlyoff the part 26, allowing for maximum accuracy and fidelity ofinformation. One option is to insulate the signal conditioning fromthermal effect by placing the signal conditioning outside the oven orautoclave. Another option is to use high temperature electronics.

In a moisture/gas flow design, a resistance or capacitance basedhumidity sensor may be mounted in line with the flow sensor.

In the high temperature (and optionally high pressure) sensor package28′ of FIG. 13, sensors are protected from high pressure by being placedinside a sealed unit, and/or are partially protected from hightemperature by being placed inside an insulated unit 60. Electronics maybe similarly protected, if necessary, from pressure and temperature.

As seen in FIG. 14, sensor packages 28 (shown in dotted outline), suchas high temperature sensor packages 28′; if placed within the oven orautoclave during cure may be attached directly to inserts such asbladders 62. A mass flow sensor 40, and its associated wiring 40 a, isshown mounted in-line on tubing 64. Tubing 64 is sized to assist inproviding laminar flow. Tubing 64 is mounted to port 62 a on bladder 62.

As seen in FIG. 15, individual flow sensors in the form of local flowsensors 72 b mounted on flow belts 72 may be placed under the vacuum bag10 (or inside the closed cavity as the case may be) to identify sourceand direction of gas flow. Thus as may be seen, bagging material 10overlays a part 66 on tool or mould 18 and is sealed to tool or mould 18by a bead of sealant 68. Vacuum is applied via vacuum hoses 30 attachedto vacuum ports 70. A breather 12 and flow belts 72 are interleavedbetween bagging material 10 and tool or mould 18. Wiring 72 a extendsfrom flow belts 72 through bagging material 10.

As seen in FIG. 15a , another option is to integrate flow sensors 40with the vacuum port 70. Thus, directional radial flow sensors 40 b,which may identify the direction from which the gas flow originates, aremounted into a vacuum port housing 70 a. A vacuum port chuck 70 b mountsonto housing 70 a so as to support a vacuum hose 30 mounted thereon andso as to seal bagging material 10 therebetween.

Flow sensors 40 mounted in sensor packages 28, may as seen in FIG. 16 beinstalled directly on, or within, the tool or mould 18 for ease of use.Thus as may be seen, again bagging material 10 overlays a part 66 ontool or mould 18 and is sealed to tool or mould 18 by a bead of sealant68. Vacuum ports 18 a are formed in tool or mould 18. Sensor packages 28are mounted in fluid communication with vacuum ports 18 a. A manifold 74is mounted to sensor packages 28 so as to connect sensor packages 28 andvacuum ports 18 a with vacuum line 30.

Software

By way of overview, one example, which is not intended to be limiting,of a high level system level software flow is shown schematically inFIG. 17, signal/data monitoring and leak localization is shown in FIGS.18a and 18b respectively, trend analysis and fingerprinting in FIG. 19,real time process simulation (of particular value when the system isused during the cure process with elevated temperature and pressure) inFIG. 20, and process control (where the process can be modified tominimize the effect of any leak or other deviation from the normalmanufacturing process) in FIG. 21. The system architecture is shown ingreater schematic detail in FIG. 22.

In FIG. 17, system level software flow 300 includes, in order ofoperation, secure login 302 which provides access to main menu 304. Mainmenu 304 provides access to system configuration 306, historicalactivities 308, or new activity 310. Historical activities 308 givesaccess to historical data actions 312 which itself provides forreporting 314 or data export 316. New activity 310 gives access toactivity configuration 318, which gives access to activities 320.Activities 320 gives access to signal or data monitoring 322, leaklocalization 324, trend analysis or fingerprinting 326, real-timeprocess simulation 328, or process control 330.

As seen in FIG. 18a , the signal/data monitoring 322 may include liveand historical sensor data 402 to provide feedback 404 which may includeplots, maps, schematics, images, sound, haptics, etc. These are used inthe determining step 406 to interrogate, analyze, probe, interact,cross-plot, etcetera, the data from step 404.

The feedback as described throughout this specification may, at least inpart, be based on, or correspond to, the spatial relationship betweenthe user/worker/inspector/receiving the feedback and the membrane ormould as the case may be.

As seen in FIG. 18b , leak localization 324 may include using live flowand pressure data 408, and the geometry and sensor location information410 to predict in step 412 the locations of one or more leaks in one ormore dimensions. Feedback is provided in step 414 using plots, maps,schematics, images, animations, projections, sounds, haptics, etceteraor any combinations thereof to show the predicted leak locations.

As seen in FIG. 19, trend analysis and finger printing 326 may includelive (that is, real-time) flow, pressure, etc. data 502, geometry andsensor location data 504, and historical data 506 from similaractivities. The data is analyzed in step 508 to combine historical dataand live data to develop trends and fingerprints for classes ofanalyses, such as finite element analysis. Feedback is provided in step510 of live data, historical envelopes, trends, fingerprints, etc. usingplots, maps, schematics, images, animations, projections, sounds,haptics, etc. or any combination thereof.

As seen in FIG. 20, real-time process simulation 328 may include livetemperature, pressure, etc. data 602, geometry and sensor location data604, and/or material data files 606. The data is analyzed in step 608 toautomatically predict material property evolution, for example theevolution of the degree of cure, viscosity, etc. Feedback is provided instep 610 of live data, predicted material properties using plots, maps,schematics, images, animations, projections, sounds, haptics, etc. orany combinations thereof to show the evolution of the materialproperties.

As seen in FIG. 21, process control 330 may include live flow, pressure,temperature, etc. data 702, geometry and sensor location data 704,process control parameters 706 and real time process simulation 328 soas to provide automated control of actuators and other process controldevices in step 708 based on measurement devices, trend analyses andprocess simulation. Feedback is provided in step 710 of the processcontrol state, actuator status, process control values, etc. usingschematics, tables, sounds, images, animations, projections, haptics,etc. or any combinations thereof.

As seen in FIG. 22, system architecture 800 includes back end 802. Backend 802 includes back end database 32. Back end database 32 communicatesvia appropriate communications protocols as would be known by oneskilled in the art, with a dispatcher or multiple dispatchers 804 andwith multiple front ends 806. Front ends 806 may include front ends 34or 36 illustrated in FIG. 2a . Dispatchers 804 communicate withelectronic packages 808 which receive data from sensor packages 810,which may include sensor packages 28.

The system level architecture described may include:

-   -   1) Use of flow and other data from multiple sensor packages,        dimensions, and materials to predict the location of a leak.    -   2) Instantaneous feedback to the users of the system, using        static and roaming devices and computers including visual,        audio, tactile, or other sensory feedback, and may also include:        -   a. the ability of the users to add comments to the system            indicating what they are doing,        -   b. the ability of the system to interface with other data            acquisition and control systems performing other factory            tasks (e.g. autoclave or oven controller).    -   3. Prediction of the type of leak(s) based on the flow behavior        or signature, for example, in the bagging material, in the tool        or moulds, in the mould or tool seal(s), in the bladder, etc.    -   4. Use of accumulated data from previously tested parts that        allow the integrated and otherwise reduced data from a range of        sensor packages to be used to characterize the evacuation        behaviour of a given part against the database, leading to        correlations with quality, herein referred to as one form of        “fingerprinting”.

As illustrated in the flow chart of FIG. 23, computationalfingerprinting 900 includes collecting geometry and sensor location data902, and material information 904, and processing that information tocreate a grid of representative virtual leak locations in step 906. Instep 908 for each virtual leak location the flow values are calculatedat sensor locations for a known virtual leak rate using a computationalmethod such as finite element analysis. In step 910 the flow value atthe virtual leak and virtual sensors are calculated and stored as a“fingerprint”. At step 912, steps 908 and 910 are iterated in loop 914until each leak location has been simulated. Once each leak location hasbeen simulated, live flow data 916 is used in comparison step 918 tofind the closest fingerprint that corresponds to the currently measuredflow data collected in step 916, so as to identify the expected leaklocation by the matching of the live flow data to the closestcorresponding fingerprint. Feedback is provided in step 920 using plots,maps, schematics, images, animation, projections, sounds, haptics, etc.,or combinations thereof.

Line leak prediction 1000 is illustrated in the flow chart of FIG. 24.Live flow data is collected in step 1002. Sensor location data iscollected in step 1004. In step 1006 curves are fitted to the live flowdata and sensor location data from steps 1002 and 1004 respectively. Instep 1008 the peaks of the curves fitted in step 1006 are identified andused to predict leak locations. Feedback is provided in step 1010 usingplots, maps, schematics, images, animations, projections, sounds,haptics, etc., or combinations thereof.

Analytical triangulation 1100 is illustrated in the flow chart of FIG.25. Analytical triangulation includes collecting live flow data in step1102 and collecting geometry and sensor location data in step 1104. Instep 1106 all possible pairs of sensors are determined from the datafrom step 1104. In step 1108, for each pair of sensors determined instep 1106, the apex of all possible triangles (so-called “apex sets”)are determined by setting the ratio of the sides of the triangles to bethe same as the ratio of the measured flows from step 1102. In step1110, for each pair of “apex sets” the point of intersection isdetermined, or where there is no intersection, the mid point of the linejoining the points of closest approach is determined so as to indicatepossible leak locations. In step 1112 the average of the possible leaklocations determined in step 1110 is used to predict a single leaklocation. The error from the scatter of possible leak locationsdetermined in step 1110 is estimated in step 1114. In step 1116 feedbackis provided using plots, maps, schematics, images, animations,projections, sounds, haptics, etc., or combinations thereof.

Test-based fingerprinting 1200 is illustrated FIG. 26. Actual geometryand sensor location data from step 1202 is used in step 1204 to lay upand bag a representative part 26 so as to create in step 1206 a grid ofrepresentative leak locations. In step 1208 a small but measurable leakis created at each representative leak location from step 1206. Themeasured leak and flow sensor data from the small leaks created in step1208 are recorded and stored in step 1210 so as to create a“fingerprint”. In step 1212, the representative leak created in step1208 is sealed and if all of the representative leak locations createdin step 1206 have not been tested then loop 1214 iterates the testing tostep 1208 for the creation of the next small but measurable leak at thenext representative leak location from the grid of representative ofleak locations created in step 1206. Live flow data collected in step1216 is used in step 1218 once all of the testing iterations of steps1208-1214 have been completed, so as to compare the data from step 1216with the fingerprints recorded and stored in step 1210 so as todetermine in step 1218 which is the closest fingerprint that correspondsto the currently measured flow data and thereby identify the expectedleak location. Feedback is provided in step 1220 using plots, maps,schematics, images, animations, projections, sounds, haptics, etc. orcombinations thereof.

Leak identification optimization 1300 is illustrated in the flow chartof FIG. 27. Geometry and vacuum lines and flow sensors data is collectedin step 1302 and used in step 1304 to create permutations of vacuum linevalve conditions. In step 1306, for each permutation in step 1304 theconditions for each valve are set. If for a particular permutation, thevalve condition, as determined in step 1308, is closed, then thevacuum/pressure is measured in step 1310, and if the valve condition isopen, gas is drawn in step 1312. Following steps either 1310 or 1312,the flow sensor data is recorded and stored in step 1314. If, asdetermined in step 1316, all of the permutations created in step 1304have not been tested, then loop 1318 returns to step 1306 so as to setthe condition for each valve in the next permutation according to thepermutations created in step 1304. Data from a previously establishedleak fingerprint data base, such as described above, is retrieved instep 1320 and, when in step 1316 it is determined that all of thepermutations have been tested, then in step 1322 the flow sensor datarecorded and stored in step 1314 is compared to the data retrieved instep 1320 so as to find the closest fingerprint that corresponds to theaggregate flow data to identify the expected leak location. Feedback isprovided in step 1324 using plots, maps, schematics, images, animations,projections, sounds, haptics, etc. or combinations thereof.

Leak fingerprint database optimization 1400 is illustrated in the flowchart of FIG. 28. Geometry and vacuum lines and flow sensors data iscollected in step 1402 and used to created permutations of vacuum linevalve conditions in step 1404. For each permutation, the condition foreach valve is set in step 1406. The valve condition for each permutationis determined in step 1408, and if the valve condition for thatpermutation is closed then vacuum/pressure is measured in step 1410. Ifthe valve condition is vented then a controlled leak (for example, asmall, measurable leak) is identified in step 1412. If the valvecondition is open then gas is drawn in step 1414. In step 1416, the flowsensor data is recorded and stored. In step 1418 it is determinedwhether each permutation created in step 104 has been tested, and ifnot, loop 1420 returns to step 1406 so as to set the condition for eachvalve for the next permutation in the permutations created in step 1404.If in step 1408 it is determined that each of the permutations has beentested then a leak fingerprint database is created or augmented in step1422.

Vacuum line and flow sensor location optimization 1500 is illustrated inthe flow chart of FIG. 29. Geometry and vacuum line and flow sensor datais gathered in step 1502. In step 1504 the fingerprint database isanalyzed so as to examine the sensitivity of flow sensor and vacuum linelocations. In step 1506 the vacuum lines and flow sensors are identifiedthat can be removed with minimal impact on the effectiveness of thesystem. In step 1508, the regions are identified where the addition ofvacuum lines and flow sensors may increase the effectiveness of thesystem.

Instead of pulling vacuum on all vacuum lines at the same time, thesystem may (automatically) turn individual vacuum lines on or off, thuseach vacuum line may either draw gas out, or become a dead end,measuring the local vacuum level/pressure. By working through allcombinations and permutations of vacuum lines being on or off,significant additional information may be generated about the locationof the leak or off-gassing. This information may be used in any one, ora combination of, the methods described previously forlocalization/triangulation/fingerprinting.

Gas paths throughout a complex part may be characterized. Instead ofhaving two options for each vacuum line (open vacuum pump or closed),each vacuum line may either be drawing vacuum, closed, or vented to theatmosphere (thus allowing air to come in). By then evaluating allcombinations, the local gas permeability's of the assembly may beevaluated, and used to calibrate thelocalization/triangulation/fingerprinting methods previously described.

Currently, to applicant's knowledge the positioning of vacuum lines isbased on experience and common sense, with no optimization. In a furtheraspect of the present invention the information gathered previously (byany of the methods, but in particular the analytical triangulation orcomputational fingerprinting) may be used to identify the sensitivity ofthe system to the number and positioning of the flow sensors.Optimization may be general, as in being sensitive to any leak oroff-gassing event, or specific, responding to the leaks or off-gassingevents that are more critical for a given part (for example ensuringthat leaks are least likely to occur in a complex zone of a part whererepair is difficult or impossible). By optimizing, the number of vacuumlines and sensors needed is minimized, and the sensitivity of thedetection for a given number of lines and sensors is maximized. Theoptimization will be part shape and size dependent, including details ofmoulds or tooling, caul plates, inserts, and bagging.

In a further embodiment each gas conduit or gas port has a correspondingunique identifier so as to correlate the gas flow data with saidcorresponding unique identifier. The unique identifier may identify aunique location and may be chosen from the group which includes, forexample, barcode, or radio-frequency identification.

In a further embodiment at least one gas conduit may be adapted to carrypower and/or data.

In the above description of the system, including in the description ofthe software processing information needed by the system (for examplethe sensor data), as will be apparent to one skilled in the art, themeaningful and efficient way to determine the output from the system,for example the feedback described above, is by the use of a digitalprocessor such as a computer. In particular in order to obtain feedbackin real time, or in a useful time to enhance production efficiency andproductivity, a digital processor is used to transform the sensor datafor example into feedback that locates gas-based defects identifiedherein.

As will be apparent to those skilled in the art in the light of theforegoing disclosure, many alterations and modifications are possible inthe practice of this invention without departing from the spirit orscope thereof. Accordingly, the scope of the invention is to beconstrued in accordance with the substance defined by the followingclaims.

What is claimed is:
 1. A process for locating a porosity-causing gasleak during manufacturing of a composite part, wherein during saidmanufacturing said part is engaged by a vacuum bag or mould so as todefine a flexible non-compartmentalized single volume containing orcovering the part and said single volume is evacuated to low pressure,and wherein the gas leak is due to a leak associated with the vacuum bagor mould such that atmospheric gas leaks into the single volume, andwherein a plurality of gas conduits cooperate in fluid communicationwith said vacuum bag or mould for flow of gas through said plurality ofgas conduits, and wherein said vacuum bag and mould is mounted so as toengage the part, and wherein a plurality of sensors are coupled incooperation with said plurality of gas conduits, and wherein saidplurality of sensors are coupled in spaced apart array relative to saidvacuum bag or mould, and wherein said plurality of sensors are in fluidcommunication with said single volume between the part and said vacuumbag or mould and wherein said plurality of sensors are adapted to detectand measure at least one of mass flow rate and/or pressure, the processcomprising: a) evacuating said single volume b) detecting and measuringsaid at least one of mass flow rate and/or pressure at least during saidevacuating of said volume, c) generating gas flow data corresponding tosaid detecting and measuring of said at least one of mass flow rateand/or pressure, d) computing gas leak information relating to one ormore of the gas leaks into said volume from said gas flow data bymethods chosen from the group consisting of: (i) localizing a leak intothe volume using the gas flow data and using the geometry of the partand sensor location information of said plurality of sensors in saidarray in relation to the part to predict locations of one or more of thegas leaks into the volume by: (a) fitting a curve to the gas flow datafor each sensor of said plurality of sensors in said array, (b)identifying a peak in each curve, (c) triangulating on the peaks, (d)predicting the leak location as corresponding to the triangulatedlocation of the peaks, (ii) localizing one or more of the gas leaks intothe volume using a profile of the gas flow data and historical recordsof past profiles of the gas flow data by: (a) recording a profile overtime of the gas flow data for the part, (b) creating and maintaining ahistorical record of the profile over time of the gas flow datacorrelated to a physical specification of the part, (c) predicting alocation of the one or more gas leaks into the single volume by: (1)comparing said recording with said historical record and locating amatching profile in said historical record matching for said part, (2)determining from said matching profile of said historical record thecorresponding leak locations, (iii) localizing one or more of the gasleaks into the volume using a profile of the gas flow data andhistorical records of past profiles of the gas flow data by: (a)creating a grid of virtual gas leak locations employing the geometry ofthe part and locations of the plurality of sensors relative to the part,and for each of the locations calculating at least the profile of thegas flow rate for a predetermined flow rate of the gas leak to predictthe gas leak information and, (b) comparing the predicted gas leakinformation to the historical records and determining a closest matchand thereby a corresponding predicted gas leak location, (iv) localizingone or more of the gas leaks into the volume using a profile of the gasflow data and historical records of past profiles of the gas flow databy: (a) creating a grid of representative gas leak locations employingthe geometry of the part and locations of the plurality of sensorsrelative to the part, and for each of the locations creating aresealable and measurable gas leak and recording corresponding gas flowdata for each of the locations to provide the historical record of thedefect information for the part, and (b) comparing the gas flow data tothe historical record for the part to determine a closest match andthereby a corresponding predicted gas leak location, and wherein saidprocess further includes optimizing a location of said at least one ofsaid plurality of sensors on said gas conduits to account for thegeometry of the part, and wherein said detecting and measuring said atleast one of mass flow rate and/or pressure in said gas conduits, andsubsequent corresponding said determination of said gas leakinformation, is detected and measured during when at least first of saidgas conduits are biased into an open-to-gas flow condition and at leastsecond of said gas conduits are biased into a closed-to-gas flowcondition during said evacuation of said volume.
 2. The process of claim1 further comprising relaying to a user feedback of said gas leakinformation, wherein said relaying of said feedback includes displayingsaid gas leak information to the user while the user is inspecting saidpart and said vacuum bag or mould, and wherein said defect gas leakinformation includes predicted leak locations computed for said at leastone gas leak.
 3. The process of claim 1 wherein said plurality ofsensors also includes at least one sensor from the group consisting ofradial flow direction sensors, humidity sensors, spectroscopic sensors.4. The process of claim 3 wherein said process includes mounting said atleast one sensor to a corresponding said at least one gas conduit. 5.The process of claim 3 wherein said plurality of sensors includes atleast one mass flow sensor, at least one pressure sensors and at leastone differential pressure sensor.
 6. The process of claim 3 furthercomprising providing a sensor package and wherein said sensor packageincludes at least two of said plurality of sensors within said package.7. The process of claim 5 further comprising providing a sensor packageand wherein said sensor package includes said mass flow sensors, saidpressure sensors and said differential pressure sensors within saidpackage.
 8. The process of claim 4 wherein at least one of saidplurality of sensors is mounted in said volume.
 9. The process of claim8 further comprising providing breather material in said volume betweensaid part and said vacuum bag or mould, wherein said breather materialhas substantially uniform permeability.
 10. The process of claim 4further comprising providing a flow bypass having a resilient flexiblebypass valve member and cooperating with at least one of said pluralityof sensors to reduce a pressure drop across at least one of saidsensors.
 11. The process of claim 3 wherein said at least one of saidplurality of sensors is coupled in cooperation with at least one of thegroup consisting of: said plurality of gas conduits, gas ports, a gasbreather, a mat having sensor flow passages, a manifold, the vacuum bagor mould.
 12. The process of claim 10 wherein said bypass valve memberincludes a reed means.
 13. The process of claim 12 wherein said reedmeans is biased between open and closed positions, according to apre-determined pressure threshold, by a gas pressure of said gas flow.14. The process of claim 13 wherein said pressure threshold is adifferential pressure threshold of a differential pressure across anassociated sensor of said plurality of sensors.
 15. The process of claim13 wherein said bypass reed means is maintained in said closed positionby a magnetic field.
 16. The process of claim 1 wherein said biasing ofsaid at least first and said at least second of said gas conduits intosaid open-to-gas flow and said closed-to-gas flow conditionsrespectively is cycled through all of said gas conduits in a pattern ofopening and closing of said gas conduits to said gas flow, wherein saidpattern provides said opening and closing in all permutations as betweenall combinations of said opening and closing of said gas conduits. 17.The process of claim 16 wherein said pattern is predetermined.
 18. Theprocess of claim 1 further comprising a flow bypass mounted in fluidcommunication with a corresponding gas conduit of said plurality of gasconduits said at least one conduit, and separate from, so as to not bemounted to said at least one sensor.
 19. The process of claim 12 whereinsaid reed means includes a curved reed, and wherein said curved reed iscurved so as to elastically pre-load said reed when in said closedposition.
 20. The process of claim 15 wherein said reed means includes acurved reed, and wherein said curved reed is curved so as to elasticallypre-load said reed when in said closed position.
 21. The process ofclaim 4 wherein said at least one sensor is adapted to measure said flowof gas both into and out of said volume.
 22. The process of claim 3wherein said plurality of gas conduits includes a corresponding at leastone inlet and/or outlet filter.
 23. The process of claim 1 whereinduring said leak detection said gas is other than air.
 24. The processof claim 1 further comprising providing a second vacuum systemindependent of said plurality of gas conduits for said evacuatingprocess, said second vacuum system mounted in a second, independent,fluid communication with said vacuum bag or mould, and furthercomprising the step of using the second vacuum system to locally changea pressure in said vacuum bag or mould so as to change a flow rate ofsaid flow of gas through said plurality of gas conduits for saidevacuating process and so as to change said flow rate of said flow ofgas interacting with said at least one of said plurality of sensors. 25.The process of claim 13 wherein said plurality of gas conduits has acorresponding unique identifier for each conduit in said at least onegas conduit so as to correlate said gas flow data with saidcorresponding unique identifier and wherein the unique identifier ischosen from the group which includes: barcodes, radio-frequencyidentification.
 26. The process of claim 1 wherein said plurality of gasconduits are adapted to carry power and/or data.
 27. The process ofclaim 1 wherein said sensors include spectroscopic sensors to providespectroscopic data for spectrographic analysis chosen from the groupconsisting of: fourier transform infrared spectroscopy, near-infraredspectroscopy.
 28. A process for locating a porosity-causing gas leakduring manufacturing of a composite part, wherein during saidmanufacturing said part is engaged by a vacuum bag or mould so as todefine a flexible non-compartmentalized single volume containing orcovering the part and said single volume is evacuated to low pressure,and wherein the gas leak is due to a leak associated with the vacuum bagor mould such that atmospheric gas leaks into the single volume, andwherein a plurality of gas conduits cooperate in fluid communicationwith said vacuum bag or mould for flow of gas through said plurality ofgas conduits, and wherein said vacuum bag and mould is mounted so as toengage the part, and wherein a plurality of sensors are coupled incooperation with said plurality of gas conduits, and wherein saidplurality of sensors are coupled in spaced apart array relative to saidvacuum bag or mould, and wherein said plurality of sensors are in fluidcommunication with said single volume between the part and said vacuumbag or mould and wherein said plurality of sensors are adapted to detectand measure at least one of mass flow rate and/or pressure, the processcomprising: a) evacuating said single volume b) detecting and measuringsaid at least one of mass flow rate and/or pressure at least during saidevacuating of said volume, c) generating gas flow data corresponding tosaid detecting and measuring of said at least one of mass flow rateand/or pressure, d) computing gas leak information relating to one ormore of the gas leaks into said volume from said gas flow data bymethods chosen from the group consisting of: (i) localizing a leak intothe volume using the gas flow data and using the geometry of the partand sensor location information of said plurality of sensors in saidarray in relation to the part to predict locations of one or more of thegas leaks into the volume by: (a) fitting a curve to the gas flow datafor each sensor of said plurality of sensors in said array, (b)identifying a peak in each curve, (c) triangulating on the peaks, (d)predicting the leak location as corresponding to the triangulatedlocation of the peaks, (ii) localizing one or more of the gas leaks intothe volume using a profile of the gas flow data and historical recordsof past profiles of the gas flow data by: (a) recording a profile overtime of the gas flow data for the part, (b) creating and maintaining ahistorical record of the profile over time of the gas flow datacorrelated to a physical specification of the part, (c) predicting alocation of the one or more gas leaks into the single volume by: (1)comparing said recording with said historical record and locating amatching profile in said historical record matching for said part, (2)determining from said matching profile of said historical record thecorresponding leak locations, (iii) localizing one or more of the gasleaks into the volume using a profile of the gas flow data andhistorical records of past profiles of the gas flow data by: (a)creating a grid of virtual gas leak locations employing the geometry ofthe part and locations of the plurality of sensors relative to the part,and for each of the locations calculating at least the profile of thegas flow rate for a predetermined flow rate of the gas leak to predictthe gas leak information and, (b) comparing the predicted gas leakinformation to the historical records and determining a closest matchand thereby a corresponding predicted gas leak location, (iv) localizingone or more of the gas leaks into the volume using a profile of the gasflow data and historical records of past profiles of the gas flow databy: (a) creating a grid of representative gas leak locations employingthe geometry of the part and locations of the plurality of sensorsrelative to the part, and for each of the locations creating aresealable and measureable gas leak and recording corresponding gas flowdata for each of the locations to provide the historical record of thedefect information for the part, and (b) comparing the gas flow data tothe historical record for the part to determine a closest match andthereby a corresponding predicted gas leak location, and wherein saidtriangulating on the peaks includes determining combinations of pairs ofsensors of said plurality of sensors by employing the geometry of saidpart and locations of said sensors relative to said part, and for eachsaid pair of sensors determine corresponding triangle apexes for alltriangles from each said pair of sensors wherein, for each said pair ofsensors, a base leg of said triangle extends to and between said pair ofsensors, and a remaining two legs of said triangle define an apexthere-between at the intersection thereof, and wherein said remainingtwo legs have first and second lengths respectively in proportion tocorresponding first and second said gas flow rates at said pair ofsensors respectively so as to determine for each said pair of sensors acorresponding set of said triangle apexes to thereby provide acorresponding apex set for said pair of sensors, for each said apex setdetermine either: a) a point of intersection between said apex sets, b)where there is no said point of intersection, a mid-point of a linejoining points closest to one another between all of said apexes toprovide possible leak locations.
 29. The process of claim 28 wherein thestep (d)(i) further comprising computing the average of said multipleleak locations to thereby predict a single leak location.